A conventional perfect binding machine comprises, for example, at least one clamp unit, a mechanism for moving the clamp unit along a path, and a series of binding units arranged under the path of the clamp unit, in which a book block is held by the clamp unit and then, while the book block is conveyed by the clamp unit along the path, the perfect binding is performed.
A glue application unit as one of the binding units is built in the perfect binding machine so as to apply glue to a back face of the book block during the passage of the clamp unit (cf. for example, Patent Document 1).
The glue application unit has a frame, a glue tank attached to the frame and filled with glue, a glue applying roller arranged in the glue tank and attached to the frame for rotation about a shaft thereof extending cross the path of the clamp, and a motor attached to the frame to rotate the glue applying roller. A lower part of the glue application roller is soaked in the glue of the glue tank and the glue application roller engages with the back face of the book block at its top face covered with the glue.
The glue application unit further comprises a wiper attached to the frame and located upstream of the top face of the glue application roller in a direction of the rotation of the glue application roller in such a way that the wiper can come into contact with and separate from the outer periphery of the glue application roller, and a wiper drive mechanism attached to the frame so as to actuate the wiper. A thickness of the glue covering the top face of the glue application roller can be adjusted by changing a distance between the outer periphery of the glue application roller and the wiper.
The glue application unit further comprises a control unit controlling the operation of the wiper drive mechanism.
Then the wiper is sequentially moved at an open position in which the wiper is separated from the outer periphery of the glue application roller by a predetermined distance and a closed position in which the wiper is made contact with the outer periphery of the glue application roller at a timing determined based on the information about a position of the book block on the path of the clamp unit, a speed of movement of the book block, a distance from the top face of the glue application roller to the wiper in a circumferential direction of the glue application roller, and a speed of the outer periphery of the glue application roller, so that the back face of the book block engages with the top face of the glue application roller covered with the glue of the predetermined thickness while the book block passes through the glue application roller.
The operation timing of the wiper will be described in more detail below with reference to accompanying drawings. FIG. 6 is a side view illustrating the operation timing of the wiper in case of rotating the glue application roller in the direction of movement of the book block.
Referring to FIG. 6A, the wiper W rotates from the closed position to the open position when the book block P reaches a position separated from the glue application roller R by a predetermined distance. Then, as shown in FIG. 6B, when the leading end of the book block P reaches the top face of the glue application roller R, the back face of the book block P engages with the top face of the glue application roller R covered with the glue G of a predetermined thickness. This engagement of the book block P with the glue application roller R continues during passage of a predetermined length of the book block P through the top face of the glue application roller R. As shown in FIG. 6C, when the predetermined length of the book block P passes through the top face of the glue application roller R, the wiper W rotates from the open position to the closed position. Thus, as shown in FIG. 6D, when the tail end of the book block P passes through the top face of the glue application roller R, the layer of the glue G on the outer periphery of the glue application roller R is cut off.
Consequently, as shown in FIG. 8A, the glue G of the predetermined thickness is applied to the back face of the book block P.
FIG. 7 is a side view illustrating the operation timing of the wiper in case of rotating the glue application roller in a direction opposite to the direction of movement of the book block P. Referring to FIG. 7A, the wiper W rotates from the closed position to the open position (a gap between the glue application roller R and the wiper W is the same as shown in FIG. 6) when the book block P reaches a position separated from the glue application roller R by a predetermined distance. Then, as shown in FIG. 7B, when the leading end of the book block P reaches the top face of the glue application roller R, the back face of the book block P engages with the top face of the glue application roller R covered with the glue G of a predetermined thickness. This engagement of the book block P with the glue application roller R continues during passage of a predetermined length of the book block P through the top face of the glue application roller R. As shown in FIG. 7C, when the predetermined length of the book block P passes through the top face of the glue application roller R, the wiper W rotates from the open position to the closed position. Thus, as shown in FIG. 7D, when the tail end of the book block P passes through the top face of the glue application roller R, the layer of the glue G on the outer periphery of the glue application roller R is cut off.
Consequently, as shown in FIG. 8B, the glue G of the predetermined thickness is applied to the back face of the book block P.
However, as can be seen in FIG. 8, in the conventional glue application unit, an amount of the glue G is more likely to be insufficient at the leading and tail end portions, in particular, the leading end portion of the back face of the book block P. The shortage of the glue applied to the leading end portion of the back face of the book block effects an incomplete filling of the glue between the book block and a cover at the leading end portion of the back face of the book block when a cover is attached to the book block in a subsequent cover attachment process, which leads to a book binding of inferior quality.